title: Heterologous expression and characterization of a malathion-hydrolyzing carboxylesterase from a thermophilic bacterium, Alicyclobacillus tengchongensis.
abstract: A carboxylesterase gene from thermophilic bacterium, Alicyclobacillus tengchongensis, was cloned and expressed in Escherichia coli BL21 (DE3). The gene coded for a 513 amino acid protein with a calculated molecular mass of 57.82 kDa. The deduced amino acid sequence had structural features highly conserved among serine hydrolases, including Ser204, Glu325, and His415 as a catalytic triad, as well as type-B carboxylesterase serine active site (FGGDPENITIGGQSAG) and type-B carboxylesterase signature 2 (EDCLYLNIWTP). The purified enzyme exhibited optimum activity with β-naphthyl acetate at 60 °C and pH 7 as well as stability at 25 °C and pH 7. One unit of the enzyme hydrolyzed 5 mg malathion l(-1) by 50 % within 25 min and 89 % within 100 min. The enzyme strongly degraded malathion and has a potential use for the detoxification of malathion residues.
authors.affiliation: College of Life Sciences, Yunnan Normal University, Kunming, Yunnan, 650500, People's Republic of China. xiezhenrong2006kycg@126.com
authors.forename: Zhenrong
authors.initials: Z
authors.lastname: Xie
authors.forename: Bo
authors.initials: B
authors.lastname: Xu
authors.forename: Junmei
authors.initials: J
authors.lastname: Ding
authors.forename: Lingyun
authors.initials: L
authors.lastname: Liu
authors.forename: Xuelin
authors.initials: X
authors.lastname: Zhang
authors.forename: Junjun
authors.initials: J
authors.lastname: Li
authors.forename: Zunxi
authors.initials: Z
authors.lastname: Huang
mesh_terms: D056450:Alicyclobacillus / Q000201:enzymology* / Q000235:genetics; D043182:Carboxylesterase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D020134:Catalytic Domain; D003001:Cloning, Molecular; D017124:Conserved Sequence; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004795:Enzyme Stability; D004926:Escherichia coli / Q000235:genetics; D015870:Gene Expression; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D008294:Malathion / Q000378:metabolism*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009284:Naphthols / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013696:Temperature
chemical_list: D004269:DNA, Bacterial; D009284:Naphthols; D011994:Recombinant Proteins; C005366:naphthyl acetate; D043182:Carboxylesterase; D008294:Malathion